Unwanted rowspan in grid table

[jgm]

Discussed in #9740

This is a table I have tried to convert to HTML, but the resulting HTML looks wrong:

+-----------------+----------+-------+------------------+
|                 | Lossless | Lossy | App              |
+=================+==========+=======+==================+
| For text        | PDF              | Preview          |
+-----------------+----------+-------+------------------+
| For images      | PNG      | JPEG  | Preview          |
|-----------------+----------+-------+------------------+
| For audio       | FLAC     | MP3   | QuickTime Player |
|-----------------+----------+-------+------------------+
| For video       | MOV              | QuickTime Player |
+-----------------+----------+-------+------------------+

In the output we have a big 3-row-span cell on the left in which "For images" and "For audio" are level-2 headers. That shouldn't happen.

Cf. #8202

[jgm]

Never mind - I see the problem. You are missing + characters in the left-hand side.